It was the start of gym class one morning last week. The Plant High School freshman was preparing to do a 1-mile fitness test on the track.

Hours later, he awoke in the hospital — recovering from sudden cardiac arrest. Curtis, 15, had collapsed as he rounded the first corner of his third lap.

On Thursday, with his arm in a sling to protect his new pacemaker, he returned to school and thanked those who saved his life.

His teacher, Carrie Mahon, was first on the scene that day. She saw Curtis go down and used her school radio to request medical assistance and ice.

"As I approached him, I knew he was really in distress," Mahon said. "I didn't know if we were going to put some ice on armpits or groin or what. But by the time I physically knelt near him, I immediately said, 'We need to call 911 right now.' "

As she waited for help, Mahon retrieved one of the school's four automated external defibrillators, or AEDs, which happened to be only a few feet away, tucked inside the track's concession stand.

With the assistance of Tampa police Officer Mark Holloway, school nurse Kayla Spilman and assistant principal Laura Figueredo, Mahon performed CPR and administered the AED.

"Charlie was such an incredible fighter that day," Mahon said. "The look on his face, the look in his eyes and the breaths that he would just fight for were so tremendously hard to take. He's the man."

Curtis was taken to Tampa General Hospital for treatment. Doctors are not sure what caused Curtis' heart to stop. His family has no history of heart disease and Curtis is active and often sails.

When he woke up, Curtis was surprised to learn what had happened.

"I was kind of in awe. How did this happen to me? I'm 15," Curtis said.

While he can't recall the events that led to the incident, Curtis said he did have an out-of-body experience as staffers performed CPR on him that day.

But, he acknowledged, he wouldn't be alive without the assistance of his teacher and staffers.

"I'm really glad they were ready for this situation," he said.

All Hillsborough County schools have at least one AED on campus. The device checks the heart's rhythm and delivers an electrical shock in an attempt to restore a normal beat.

Curtis' parents said they now understand the importance of having the devices everywhere.

"Trained staff around our children and an AED device can save and will save lives," said his father, Chuck Curtis. "There are not devices everywhere. That is something we can control, and it will save lives."